Aquatic Ecosystems PDF

3 Aquatic Ecosystems BEFORE YOU READ WHAT YOU’LL LEARN On the lines below, list some characteristics of a body of water how depth and water flow...

3 Aquatic Ecosystems BEFORE YOU READ WHAT YOU’LL LEARN On the lines below, list some characteristics of a body of water how depth and water flow affect freshwater ecosystems near you. How deep is it? Is the water salty? Is it calm or fast flowing? Then read the lesson to learn the characteristics of the zones of marine ecosystems different water ecosystems. how to identify transitional aquatic ecosystems READ TO LEARN ⊳ FOCUS The Water on Earth Think of a quiz question for each paragraph. Write the Most of Earth is covered with water. Aquatic ecosystems question on one side of a flash card. Write the answer on the include freshwater, transitional, and marine ecosystems. other side. Use the flash cards to quiz yourself until you know Freshwater Ecosystems all the answers. Ponds, lakes, streams, rivers, and wetlands are freshwater ecosystems. The graph on the left below shows that only about TAKE A LOOK 2.5 percent of Earth’s water is freshwater. The graph on the right 1. Calculate the percentage of shows that 68.9 percent of the freshwater is contained in glaciers, freshwater that is not ice. 30.8 percent is groundwater, and 0.3 percent is found in lakes, Show your work. ponds, rivers, streams, and wetlands. Almost all freshwater species live in the 0.3 percent. Copyright © McGraw-Hill Education Earth’s water Freshwater Get It? 2. Infer how climate change 97.5% will likely change the graph. Saltwater 68.9% 2.5% 30.8% Freshwater Glaciers Groundwater 0.3% Lakes and rivers Reading Essentials Communities, Biomes, and Ecosystems 29  What affects water flow in rivers and streams? The water in rivers and streams flows in one direction. As illustrated in the figure below, the water flow begins at a source called a headwater. The water flows to the mouth, where it empties into a larger body of water. Rivers and streams also might start from underground springs or from melting snow. The slope of the land determines direction and speed of the water flow. Water flows quickly down a steep slope. Fast-flowing water picks up a lot of sediment. Sediment is material left by water, wind, or glaciers. As the slope levels, the fast-flowing water slows. This causes the sediment to be deposited in the form of sand, silt, and clay. Rivers and streams change during their journey from source to mouth. Wind stirs up the water’s surface and adds oxygen to the TAKE A LOOK water. Water erodes the land, changing the path of the river or 3. Label the area of the river stream. where most sediment will Currents of fast-moving rivers and streams prevent organic be deposited. On the lines below, explain why. materials and sediments from building up. As a result, fewer species live in rapid waters. Organisms living in rivers and streams must be able to withstand the water current. Plants take root in streambeds where rocks and sand bars slow the water flow. In slow-moving water, insect eggs and larvae are the main food source for many fish. Calm water also provides a home for crabs, tadpoles, and frogs. Headwater River Estuary region Copyright © McGraw-Hill Education Lake Mouth What are the characteristics of lakes and ponds? An inland body of standing water is called a lake or pond. Nutrient-poor lakes, called oligotrophic (uh lih goh TROH fihk) lakes, are often found high in the mountains. Few plant and animal species live in these lakes. Many plant and animal species live in nutrient-rich lakes, called eutrophic (yoo TROH fihk) lakes, are often found at lower elevations. Reading Essentials Communities, Biomes, and Ecosystems 30  Lakes and ponds are divided into three zones that are determined by depth and distance from the shoreline. The area closest to shore is the littoral (LIH tuh rul) zone. Species in this zone include algae, rooted and floating plants, snails, clams, insects, fishes, and amphibians. Some insect species lay eggs in the littoral zone and the larvae develop there. The limnetic (lihm NEH tihk) zone is the open water area. It is well lit and full of plankton. Plankton are free-floating organisms THINK IT OVER that live in freshwater or marine ecosystems. Many species of 4. Explain why you would freshwater fish live in the limnetic zone because food is plentiful expect to find few plankton there. in the profundal zone. The deepest area of a lake is the profundal (pruh FUN dul) zone. It is much colder and has less oxygen than the other two zones. Less light reaches the profundal zone, which limits the species that are able to live there. Marine Ecosystems THINK IT OVER 5. Describe two important Marine ecosystems have a major impact on the planet. For ways that marine example, marine algae consume large amounts of carbon dioxide ecosystems impact the from the atmosphere. In the process, they supply much of the planet. oxygen in the atmosphere. Also, water that evaporates from the oceans eventually provides most of Earth’s precipitation—rain and snow. Oceans are separated into zones, as shown in the figure below. How do the tides affect the intertidal zone? The intertidal (ihn tur TY dul) zone is a narrow band where the ocean meets land. As tides and waves move in, the intertidal zone is submerged. As tides and waves move out, the intertidal zone is exposed. Only a few species of algae and mollusks live where the Copyright © McGraw-Hill Education highest tides reach. A diversity of species, including algae and small animals such as snails, crabs, sea stars, and fishes, live in Get It? 6. Describe environmental areas that are submerged during high tide. The bottom of the variation in intertidal zones. intertidal zone is exposed only during the lowest tides. Many species of invertebrates, fishes, and seaweed live here. On sandy coasts, waves constantly shift the sand. The constant shifting makes it hard for algae and plants to grow here. Animals that live on beaches include worms, clams, predatory crustaceans, crabs, and shorebirds. Reading Essentials Communities, Biomes, and Ecosystems 31  Spray zone High-tide zone High tide Mid-tide zone Low tide Low-tide zone How do layers of the open ocean differ? The open ocean is divided into the pelagic (puh LAY jihk) zone, abyssal (uh BIH sul) zone, and benthic zone. The photic zone is the area in the pelagic zone from the surface of the water down to about 200 m. The photic zone is shallow enough for sunlight to penetrate. As depth increases, light decreases. The photic zone supports seaweed, plankton, fishes, jellyfish, and dolphins. Below the photic zone lies the aphotic zone where sunlight cannot penetrate. This region of the pelagic zone remains in constant darkness. Organisms that depend on sunlight for energy cannot live in the aphotic zone. Copyright © McGraw-Hill Education The benthic zone is the area along the ocean floor. It consists of sand, silt, and dead organisms. In shallow areas, sunlight can penetrate to the ocean floor. As depth increases, less sunlight can penetrate, and temperatures decrease. As a result, species diversity also decreases as depth increases. Many species of bacteria, fungi, sponges, sea anemones, and fishes live in shallower parts of the benthic zone. THINK IT OVER The abyssal zone is the deepest region of the ocean. The water 7. Name two limiting factors as depth increases in the is very cold. Most organisms depend on pieces of food that drift benthic zone. down from the zones above. Hydrothermal vents on the seafloor release hot water, hydrogen sulfide, and other minerals. Communities of bacteria live around these vents. These bacteria can use the sulfide molecules for energy. Reading Essentials Communities, Biomes, and Ecosystems 32  What organisms do coral reefs support? A coral reef is an ecosystem that exists in warm, shallow marine waters. The hard, stony structure of the reef is formed by secretions of tiny animals—coral polyps. Most coral polyps have a symbiotic relationship with algae. The algae provide corals with food. In turn, the corals provide algae with protection and access to light. Corals also feed by extending tentacles to catch plankton. Sea slugs, octopuses, sea urchins, sea stars, and fishes are part of the great diversity of the coral reef. THINK IT OVER Like all ecosystems, a coral reef is sensitive to changes in the 8. Define What is a coral? environment. A natural event such as a tsunami as well as human (Circle your answer.) activity such as land development can damage or kill a coral reef. a. a plant Ecologists monitor coral reef environments to help protect them b. an animal from harm. c. a colorful shell Transitional Aquatic Ecosystems Transitional aquatic ecosystems are a combination of two or more different environments. Transitional aquatic ecosystems can be areas where land and water mingle. They can also be areas where salt water and freshwater mix. Examples of transitional aquatic ecosystems are wetlands and estuaries. What kinds of life thrive in wetlands? Wetlands are areas of land that are saturated with water and support aquatic plants. Examples include marshes, swamps, and bogs. Bogs are wet and spongy areas of decomposing vegetation. Wetlands support a diversity of species. Pond lilies, cattails, amphibians, reptiles, birds, and mammals live in wetlands. How do estuaries differ from wetlands? Copyright © McGraw-Hill Education An estuary (ES chuh wer ee) is an ecosystem that forms where a freshwater river or stream merges with the ocean. The mixing of waters with different salt concentrations creates a unique ecosystem. Algae, seaweed, and marsh grasses thrive in estuaries. THINK IT OVER 9. Contrast How do estuaries Animals such as worms, oysters, and crabs feed on tiny organic differ from wetlands? matter called detritus (dih TRY tus). Many species of fishes, shrimp, ducks, and geese use estuaries as nurseries for their young. Salt marshes are transitional ecosystems similar to estuaries. Salt-tolerant grasses live along the shoreline. Animals such as shrimp and shellfish live in salt marshes. Reading Essentials Communities, Biomes, and Ecosystems 33